====== X11 ======
  * [[https://www.x.org/wiki/|x.org]]
  * 教程：[[https://tronche.com/gui/x/]]
  * [[https://silaoa.github.io/2020/2020-04-25-Cygwin%E7%B3%BB%E5%88%97%EF%BC%88%E5%8D%81%E4%BA%8C%EF%BC%89%EF%BC%9A%E4%BA%86%E8%A7%A3X.html|了解X系统]]

===== Tips =====
  * X11没有topmost, 参考[[https://tronche.com/gui/x/xlib/window/configure.html#XWindowChanges|XWindowChanges]]
  * 列举窗口示例, 编译指令 ''g++ -lX11 list_win.cpp -o list_win''<code c++>
#include <X11/Xlib.h>
#include <iostream>

int main()
{
    auto display = XOpenDisplay(nullptr);
    auto root_window = DefaultRootWindow(display);

    Window root_return, parent_return;
    Window * child_list = nullptr;
    unsigned int child_num = 0;
    XQueryTree(display, root_window, &root_return, &parent_return, &child_list, &child_num);

    for(unsigned int i = 0; i < child_num; ++i) {
        auto window = child_list[i];
        XWindowAttributes attrs;
        char* title = nullptr;
        XGetWindowAttributes(display, window, &attrs);
        XFetchName(display, window, &title);
        std::cout << "#" << i <<":" << "(" << attrs.width << ", " << attrs.height << ")";
        if(title){
                std::cout << title;
        }
        std::cout  << std::endl;
        XFree(title);
    }

    XFree(child_list);
    XCloseDisplay(display);

    return 0;
}

</code>
     * https://linux.die.net/man/3/xquerytree